Wicking condensate evaporator for an air conditioning system

ABSTRACT

One embodiment of the present invention provides an air conditioning (AC) system that evaporates its own condensate. This AC system includes a condenser coil and an evaporator coil that produces condensate. The AC system also includes a wicking-evaporative device that is configured to wick and evaporate the condensate in the vicinity of the condenser coil.

RELATED APPLICATION

This application hereby claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application No. 61/154,720, filed on 23 Feb. 2009,entitled “WICKING CONDENSATE EVAPORATOR AT AC CONDENSER,” by inventorsRichard C. Bourne. (Attorney Docket No. UC08-399-2PSP).

BACKGROUND

1. Field of the Invention

The present invention generally relates to design of air conditioning(AC) systems. More specifically, the present invention relates totechniques for improving efficiency and reducing the cost of AC-systeminstallations by evaporating condensate at the AC system's condensercoil.

2. Related Art

Both residential and commercial air conditioning (“AC”) systemstypically condense moisture on the cooling coil, known as the system'sevaporator (also referred to as the “evaporator coil”). The resultingwater, referred to as “condensate,” is then drained through pipes eitherto the ground, which is commonly done in residential systems, or to astorm or sanitary drain system, which is commonly done in commercialsystems. Note that the plumbing for draining of the condensate adds costto each AC system. However, if the condensate can be re-evaporated atthe AC system, the piping cost can be eliminated. Moreover, if suchevaporation takes place at the AC system's heat discharge coil, alsoknown as the “condenser coil,” the energy consumption associated withrejecting heat at the condenser coil, can be reduced.

There are existing techniques for re-evaporating the AC condensate atthe condenser coil of an AC system. For example, one technique uses asmall pump placed below the condensate collection pan to pump condensatethrough piping to the top of a drip-type evaporative media. Anothertechnique uses a device to create a “mist” in an air stream which can bedirected onto the condenser coil without the need for evaporative media.However, both of these existing techniques require electrical componentsand electrical power to operate, and therefore introduce additionalcomponent costs, the need for specialized electricians for fieldinstallations, and associated maintenance and replacement costs.

Hence, what is needed is a technique for re-evaporating the ACcondensate at the condenser coil of an AC system without theabove-described problems.

SUMMARY

One embodiment of the present invention provides an air conditioning(AC) system that evaporates its own condensate. This AC system includesa condenser coil and an evaporator coil that produces condensate. The ACsystem also includes a wicking-evaporative device that is configured towick and evaporate the condensate in the vicinity of the condenser coil.

In some embodiments, the AC system also includes a tray system that isconfigured to collect the condensate.

In some embodiments, the tray system is positioned at the base of thecondenser coil and distributes the condensate laterally along the widthof the condenser coil.

In some embodiments, the wicking-evaporative device includes a firstmaterial that wicks the condensate upward from the tray system.

In some embodiments, the wicking-evaporative device is positioned in thetray system such that a lower portion of the first material is immersedin the condensate.

In some embodiments, the wicking-evaporative device is positioned suchthat an upper portion of the first material is disposed upward above thesurface of the condensate, and the condensate is wicked from the lowerportion of the first material to the upper portion of the firstmaterial.

In some embodiments, the upper portion of the first material ispositioned on the air inlet side of the condenser coil.

In some embodiments, the upper portion of the first material ispositioned in the path of an airflow that is directed toward thecondenser coil. Consequently, the airflow facilitates evaporating thecondensate that is wicked into the upper portion of the first material.

In some embodiments, the first material is constructed into a set ofspaced wicking sheets which are arranged laterally along the width ofthe condenser coil.

In some embodiments, the first material is configured so that itsdimension perpendicular to the condenser coil is greater than the heightof the first material.

In some embodiments, the first material is a wicking material.

In some embodiments, the first material is a polyvinyl alcohol(PVA)-based material.

In some embodiments, the wicking material is made of wicking fibers.

In some embodiments, the wicking fibers are oriented upward from thetray system.

In some embodiments, pore sizes of the wicking fibers decrease withdistance away from the tray system.

In some embodiments, the first material is configured to wick thecondensate at a rate substantially equal to a maximum expectedcondensation rate at the evaporator coil.

In some embodiments, the first material is configured to reduce airflowresistance through the wicking-evaporative device.

In some embodiments, the wicking-evaporative device includes a secondmaterial that distributes the condensate laterally along the width ofthe condenser coil.

In some embodiments, the wicking-evaporative device is positioned in thetray system such that a lower portion of the second material is immersedin the condensate.

In some embodiments, the wicking-evaporative device is positioned in thetray system such that the second material is located entirely above thesurface of the condensate in the tray system.

In some embodiments, the wicking-evaporative device is positioned suchthat an upper portion of the second material is disposed upward andpositioned in front of the condenser coil.

In some embodiments, the upper portion of the second material ispositioned in the path of an airflow which is directed toward thecondenser coil. Consequently, the airflow facilitates evaporating thecondensate which is spread into the upper portion of the secondmaterial.

In some embodiments, the second material includes evaporative media.

In some embodiments, the evaporative media include corrugated paper.

In some embodiments, the second material is configured to distribute thecondensate laterally at a rate substantially equal to a maximum expectedcondensation rate.

In some embodiments, the second material is configured to reduce airflowresistance through the wicking-evaporative device.

In some embodiments, the first material is distributed in a uniformpattern within the second material.

In some embodiments, the wicking-evaporative device is constructed intoalternating layers, wherein a pair of adjacent layers includes a firstlayer made of the first material and a second layer made of the secondmaterial. The first layer and the second layer are in contact with eachother.

In some embodiments, the first material is interspersed with the secondmaterial.

In some embodiments, a combination of the first material and the secondmaterial is configured to minimize airflow resistance.

In some embodiments, the first material and the second material are thesame type of material.

In some embodiments, the tray system includes a first tray and a secondtray that are interconnected but spaced apart from each other. Further,the second material is positioned between the first tray and the secondtray, and the first material is positioned to wick the condensate fromboth trays to the second material.

In some embodiments, the second material is located entirely above thehighest water level in the first tray and the second tray.

In some embodiments, the tray system has a capacity substantially equalto a maximum expected volume of surplus water accumulated when thecondensation rate at the evaporator coil exceeds the evaporation rate atthe wicking-evaporative device.

In some embodiments, the wicking-evaporative device is configured towick the condensate at an angle that is within a range from the verticaldirection and the horizontal direction.

In some embodiments, evaporating the condensate in the vicinity of thecondenser coil facilitates cooling the condenser coil.

In some embodiments, evaporating the condensate in the vicinity of thecondenser coil eliminates a need for piping to drain the condensate awayfrom the AC system.

One embodiment of the present invention provides a wicking-evaporativedevice for removing condensate collected from an evaporator coil withinan AC system. During operation, the wicking-evaporative device wicks thecondensate upward into evaporative media that is positioned in the pathof an airflow directed toward a condenser coil of the AC system. Next,the evaporative media and the airflow facilitate evaporating thecondensate in the vicinity of the condenser coil, thereby eliminatingthe need for piping to drain the condensate away from the AC equipment.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 presents a schematic illustrating an air conditioning (AC) systemwhich pipes the condensate to drain.

FIG. 2 presents a schematic illustrating a cross-section of an AC systemwhich re-evaporates condensate in accordance with an embodiment of thepresent invention.

FIG. 3 illustrates a 3-dimensional (3D) model of the wicking-evaporativedevice in accordance with an embodiment of the present invention.

FIG. 4A illustrates a cross-section in the horizontal direction of anexemplary design of the wicking-evaporative device based on a singlewicking material in accordance with an embodiment of the presentinvention.

FIG. 4B illustrates a cross-section in the vertical direction of theexemplary design in FIG. 4A wherein wicking material 402 is shown in theform of wicking sheets.

FIG. 5A illustrates a cross-section in the horizontal direction of anexemplary design of the wicking-evaporative device which uses a firstmaterial for wicking condensate in the vertical direction and a secondmaterial for spreading condensate in the lateral direction in accordancewith an embodiment of the present invention.

FIG. 5B illustrates a cross-section of another design of thewicking-evaporative device based on the first material and the secondmaterial in accordance with an embodiment of the present invention.

FIG. 6 illustrates a cross-section in the vertical direction (top-view)of an exemplary design of the wicking-evaporative device based on asingle or two-material wicking material in accordance with an embodimentof the present invention.

FIG. 7 illustrates an exemplary configuration of a tray and awicking-evaporative device in an AC system in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Some embodiments of the present invention provide wicking-evaporationtechniques for re-evaporating AC condensate at the condenser coil of anAC system. The present techniques do not require electrical componentsor electrical energy to operate, thus eliminating the cost of amotorized component, the cost of specialized electrician labor forinstallation, and the maintenance and replacement costs associated withan electrical device.

More specifically, some embodiments of the present invention disposewicking-evaporative media within a portion of the condenser airflow atthe bottom of the condenser coil. Furthermore, a tray is provided whichsupports or contacts the lower edge of the wicking-evaporative media,and the bottom of the tray is positioned lower than the drain line fromthe condensate collection pan at the evaporator side. The condensate isthen piped to the tray, and wicked upward through thewicking-evaporative media to evaporate into the condenser airflow.

FIG. 1 presents a schematic illustrating an air conditioning (AC) system100 which pipes the condensate to drain.

AC system 100, for example a rooftop AC unit, includes a compressor 102,a condenser 104, an expansion valve 106, and an evaporator 108. Thesecomponents are connected by tubing to form a loop through which arefrigerant circulates during a cooling cycling. Typically, arefrigerant enters compressor 102 in a vapor form and exits compressor102 as superheated vapor. This superheated vapor travels throughcondenser 104 which condenses the vapor into a liquid; in doing so, theheat is transferred to condenser 104. The liquid refrigerant entersexpansion valve 106 which causes a portion of the liquid to vaporize.This creates a mixture of liquid and vapor at a cooler temperature. Thecold liquid-vapor mixture then travels through the evaporator coil ofevaporator 108 and is substantially vaporized by cooling the warm airbeing blown through evaporator 108. This process additionally condensesmoisture from the warm air onto the evaporator coil to form condensate.The resulting refrigerant vapor returns to compressor 102 to complete acooling cycle and start the next cooling cycle. Note that the condensateis drained through piping 110 either to the ground or away from ACsystem 100.

FIG. 2 presents a schematic illustrating a cross-section of an AC system200 which re-evaporates the condensate in accordance with an embodimentof the present invention.

As illustrated in FIG. 2, a vertical direction 202 represents the upwarddirection along the height of AC system 200, and a horizontal direction204 represents the direction of airflow of incoming air 211 (i.e., theair inlet to the condenser) which is used to cool condenser coil 210(from right to left in this case). A third direction, referred to as“lateral direction” 206, is perpendicular to the paper and parallel tothe width of AC system 200 and the width of condenser coil 210 (notshown). Although not shown, condenser coil 210 typically has an extendedprofile in lateral direction 206. Note that the above definitions forthe three directions are also used throughout the discussion below whena same-named direction is referred.

AC system 200 also includes an evaporator coil 208, a condenser coil 210and a housing 203. Evaporator coil 208 is located at the far left ofhousing 203 and is open to both the air flows inside of AC system 200and outside of AC system 200. During operation, warm air 205 which isdriven by fan 207 flows from right to left onto evaporator coil 208,while cool air 209 flows from right to left out of evaporator coil 208to cool a space outside of AC system 200. Condenser coil 210 is locatedat the far right of housing 203 and is open to both the air flows insideof AC system 200 and outside of AC system 200. As is mentioned above,condenser coil 210 also has an extended width in lateral direction 206.During operation, incoming air 211 from outside of AC system 200 flowsfrom right to left through condenser coil 210 to cool the condensercoil. This incoming air flow may be caused by a lower pressure createdwithin AC system 200. Typically, incoming air 211 becomes exhaust air213 after passing through condenser coil 210 and is vented out of ACsystem 200. Note that some of the AC system components, such as thecompressor and the expansion valve, are not shown in FIG. 2.

AC system 200 also includes a condensate-collection mechanism 214 whichcollects condensate at evaporator coil 208. Embodiments of the presentinvention also provide a tube 215 which guides the condensate fromevaporator coil 208 into tray 216. As illustrated in FIG. 2, tray 216 isplaced at the base of condenser coil 210 and is configured to holdcondensate 218. Note that tube 215 may guide the flow of the condensatethrough gravity. For example, tube 215 may be angled slightly downwardfrom the evaporator side to the condenser side. In some embodiments,instead of using a tube, an open channel or a pan may be used to guidethe condensate into tray 216. Note that, while different designs of aguiding mechanism may be used in place of tube 215, no power is requiredto drain the condensate into tray 216.

Note that in other embodiments tray 216 may be alternatively implementedas any type of water container which has an opening. Moreover, a singletray 216 may be replaced by two or more interconnected trays to increasecondensate-collection capacity. In some embodiments, acondensate-collection tray can also be placed at the base of evaporationcoil 208 between condensate-collection mechanism 214 and tube 215.However, in these embodiments, the bottom of tray 216 may need to bepositioned lower than the drain line of the condensate-collection trayat the evaporator side.

In some embodiments, tray 216 is sized to collect the maximum expectedvolume of condensate without spilling. This maximum expected volume maybe measured at conditions when the condensation rate at the evaporatorcoil exceeds a current evaporative capability. For example, suchconditions can occur when warm air 205 has a high humidity andtemperature, which leads to a high condensation rate and a surplus ofwater flowing into tray 216. In some embodiments, a simulation tool maybe used to predict a condensation rate at the evaporator coil based onboth indoor and outdoor conditions.

While FIG. 2 illustrates tray 216 as separate from housing 203, in someembodiments, tray 216 may be integrated with housing 203. Moreover,while FIG. 2 illustrates tray 216 as outside of housing 203, in someembodiments, tray 216 may be placed partially or entirely inside housing203 within a space between condenser coil 210 and the bottom of housing203.

Note that, while FIG. 2 provides a cross-section view of tray 216, tray216 also has a width in lateral direction 206. In some embodiments, thewidth of tray 216 is substantially equal to the width of condenser coil210 in lateral direction 206. Note that in these embodiments tray 216evenly distributes condensate 218 in lateral direction 206 along thewidth of condenser coil 210.

Some embodiments of the present invention also provide awicking-evaporative device 220. As illustrated in FIG. 2,wicking-evaporative device 220 is positioned such that a lower portionof wicking-evaporative device 220 is placed within tray 216 and theremainder of wicking-evaporative device 220 is disposed upward into theair stream of incoming air 211. Hence, wicking-evaporative device 220 isalso partially immersed in condensate 218. Note that whilewicking-evaporative device 220 is shown to be in contact with the bottomof tray 216, other embodiments can also have wicking-evaporative device220 suspended in condensate 218. This can be achieved by affixedwicking-evaporative device 220 onto to the sidewalls of tray 216.

In one embodiment, wicking-evaporative device 220 is configured to wickcondensate 218 upward from a lower portion of wicking-evaporative device220 into an upper portion of wicking-evaporative device 220, which ispositioned in the path of incoming air 211. The effect of wicking isindicated by a arrow 222 pointing at the highest level of the wicked-upcondensate. As shown in FIG. 2, the wicked-up condensate is directly inthe path of incoming air 211, which facilitates evaporation of thewicked-up condensate into water vapor. Because wicking-evaporativedevice 220 allows incoming air 211 to flow through, the water vapormoves along with incoming air 211 onto condenser coil 210 (and the finsof the condenser), helping to cool condenser coil 210 in the process.Additionally, after taking part in the evaporation process, incoming air211 is further cooled down when reaching condenser coil 210.Consequently, the efficiency of incoming air 211 in cooling condensercoil 210 can be significantly increased.

Note that some embodiments of the present invention take advantage ofthe existing cooling airflow of a conventional AC system to facilitateevaporation of the condensate. Therefore, the condensate evaporation andthe improved cooling efficiency are acquired without requiringadditional electrical power. Although evaporation of the condensate as aresult of direct heat radiation from the hot condenser coil may be alesser effect, it can also contribute to the overall evaporation rate ofcondensate 218. The evaporation rate due to this effect may be furtherincreased by reducing the distance between condenser coil 210 andwicking-evaporative device 220. In some embodiments, wicking-evaporativedevice 220 and condenser coil 210 are in direct contact with each other.

Note that, when AC system 200 is in normal operation, theabove-described process of condensate collection into tray 216, theprocess of condensate wicking, and the process of condensate evaporationbecome automatic and can occur indefinitely without requiring additionalelectrical power. In other words, the condensation wicking-evaporatingprocess of the present invention becomes an integral part of the coolingcycles of AC system 200.

FIG. 3 illustrates a 3-dimensional (3D) model of wicking-evaporativedevice 220 in accordance with an embodiment of the present invention. Inthis simplified model, wicking-evaporative device 220 may be representedby a plate structure associated with a height 302 in the verticaldirection, a thickness 304 in the horizontal direction, and a width 306in the lateral direction. Note that each direction in FIG. 3 has thesame meaning as a corresponding direction with the same name in FIG. 2.Also, FIG. 3 is understood and discussed in conjunction with FIG. 2.

Typically, height 302 of wicking-evaporative device 220 is designed sothat at least an upper portion of wicking-evaporative device 220 ispositioned in the path of incoming air 211. As a result, at least aportion of incoming air 211 first blows through wicking-evaporativedevice 220 before reaching condenser coil 210 behind wicking-evaporativedevice 220. Generally, the top of wicking-evaporative device 220 may bedesigned to be anywhere between the top and bottom of the condenser coil210.

In the horizontal direction, wicking-evaporative device 220 is designedto allow incoming air 211 to flow through. In some embodiments,wicking-evaporative device 220 has a structure in the horizontaldirection which facilitates minimizing the pressure drop of incoming air211 through the device, in other words, providing a least airflowresistance in that direction. Consequently, thickness 304 ofwicking-evaporative device 220 along the horizontal direction istypically much smaller than its height 302 and width 306.

In the lateral direction, wicking-evaporative device 220 is designed tohave a width to facilitate wicking up a maximum volume of thecondensate. In some embodiments, width 306 may be comparable to thewidth of tray 216 or condenser coil 210.

Although FIG. 3 models wicking-evaporative device 220 as a singlecontinuous structure, some embodiments may use two or more laterallyisolated plate structures in the lateral direction, wherein each platestructure only occupies a portion of the full tray length. Also notethat, while the model for wicking-evaporative device 220 is shown with auniform box structure, some embodiments may constructwicking-evaporative device 220 in other geometries. For example, insteadof constructing a rectangular cross-section in the lateral direction,this cross-section may be constructed in a trapezoidal shape with thetop edge narrower than the bottom edge.

In some embodiments, wicking-evaporative device 220 is formed by atleast a wicking material which is responsible for the wicking action ofwicking-evaporative device 220. More specifically, the wicking materialis partially immersed in the condensate in the tray, and is configuredto wick water from the tray upward toward the top of wicking-evaporativedevice 220 and into the path of incoming air 211. Generally, anymaterial that is capable of moving water through capillary action can beused as the wick material in wicking-evaporative device 220. Forexample, a polyvinyl alcohol (PVA)-based material can be used as thewicking material. Such material can be made of hollow wicking fibers orwicking tubes. Furthermore, the wick material can be made of a singlewick material or a composite wicking material containing two or moretypes of wicking material.

In some embodiments, designing wicking-evaporative device 220 involvesattempting to achieve the follow objectives: (1) maximizing theevaporation rate; and (2) minimizing air flow resistance. Note that toachieve the first objective one can attempt to maximize the verticalwicking rate of the wicking material and/or to maximize surface area ofwicking-evaporative device 220 which faces incoming air 211.

FIG. 4A illustrates a cross-section in the horizontal direction of anexemplary design of wicking-evaporative device 220 based on a singlewicking material 402 in accordance with an embodiment of the presentinvention. In the design of FIG. 4A, wicking material 402 is constructedas an array of long wicking tubes arranged along the width ofwicking-evaporative device 220, wherein each wicking tube is orientedupward along the vertical direction. In one embodiment, the array ofwicking tubes is affixed within a frame 408.

In this design, the wicking tubes are separated by spaces to allowincoming air to flow through. This is necessary because the wickingtubes themselves may have large airflow resistance. Note that, whilewicking material 402 can be represented as wicking tubes in thecross-section view, it is typically made into wicking sheets in thehorizontal direction so that wicking material 402 occupies the fullthickness of wicking-evaporative device 220 in that direction. FIG. 4Billustrates a cross-section in the vertical direction of the exemplarydesign in FIG. 4A wherein wicking material 402 is shown as wickingsheets. Hence, we use the term “wicking tubes” to specifically refer tothe cross-section of the wicking sheets in the horizontal direction.

Referring back to FIG. 4A, note that to maximize the vertical wickingrate one can choose one or more of the following strategies: (1) using agreater number of wicking tubes; and/or (2) using wicking tubes withlarger pore sizes. However, both of these strategies also reduce airgaps between the wicking tubes, which can lead to a higher airflowresistance of wicking material 402. Therefore, there is a trade-offbetween maximizing the wicking rate and minimizing airflow resistancefor the design of FIG. 4A.

In some embodiments, instead of attempting to achieve a maximum wickingrate, wicking material 402 is configured to only wick water at a maximumexpected condensation rate. In these embodiments, the system ensuresthat wicking and evaporation can generally exceed the condensation ratewhile avoiding using excessive wicking material.

While FIG. 4A illustrates wicking tubes having uniform pore sizes, someembodiments can use wicking tubes with varying pore sizes. Typically,large pore sizes facilitate wicking a greater volume of water but do notsupport a large wicking height in the vertical direction. On the otherhand, small pore sizes facilitate increasing wicking height but tend towick a lesser volume of water. Hence, one can build the wicking tubeswherein the pore sizes vary as a function of height. For example, eachwicking tube can have a gradually shrinking pore size from the bottom ofthe wicking tube to the top of the wicking tube. Such a design may allowmore condensate to be wicked to a greater wicking height.

Note that FIG. 4A includes a line marking 404 which represents the topwater level in the tray. FIG. 4A also includes a line marking 406 whichrepresents the highest level of the wicked-up condensate due to theeffect of wicking material 402. However, the position of line marking406 can change as a result of a number of factors. These factors caninclude, but are not limited to: temperature, humidity, volume ofcondensate in the tray, and the type and structure of the wickingmaterial 402. While wicking material 402 is responsible for distributingthe condensate in the vertical direction, the wicking material itselfmay not be capable of evaporating the wicked-up condensate efficiently.

FIG. 5A illustrates a cross-section in the horizontal direction of anexemplary design of wicking-evaporative device 220 which uses a firstmaterial for wicking condensate in the vertical direction and a secondmaterial for spreading condensate in the lateral direction in accordancewith an embodiment of the present invention. More specifically,wicking-evaporative device 220 comprises an array of long wicking sheets502 (in the 3D structure) which are made of a first material. Wickingsheets 502 are partially submerged in the condensate (line marking 504indicates the top water level in the tray) and wick the condensate inthe vertical direction.

Wicking-evaporative device 220 also comprises, within the spacingbetween a pair of wicking sheets 502, evaporative media 506 which aremade of a second material. Note that evaporative media 506 have acorrugate structure and hence a very large surface area. The corrugatedstructure of evaporative media 506 also facilitates making multiplecontacts with adjacent wicking sheets 502. In doing so, evaporativemedia 506 draw water from wicking sheets 502 and distribute the waterlaterally in the spaces between wicking sheets 502. As a result, thecombined structure of wicking sheets 502 and evaporative media 506creates a much larger surface area for distributing the condensate ascompared to the design in FIG. 4A. The large surface area of theresulting wicking-evaporative device 220 significantly increases theevaporation rate when such a device is installed in an AC system.Furthermore, because the corrugated structure of evaporative media 506is configured to have a low airflow resistance, this design facilitatesachieving both maximum evaporation and minimum airflow resistance at thesame time. In one embodiment, wicking sheets 502 and evaporative media506 are securely attached onto a frame 507.

The second material of evaporative media 506 can include both a wickingmaterial and a non-wicking material. If the second material is a wickingmaterial, it can be the same type of material as the first material. Inone embodiment, the second material is a CELdek™ evaporative media. Inanother embodiment, evaporative media 506 is made of corrugated paper.

In the design of FIG. 5A, evaporative media 506 have the same height aswicking sheets 502, and therefore are also partially submerged in thecondensate. In this design, evaporative media 506 can provide limitedvertical wicking action but are not the main wicking media. FIG. 5Billustrates a cross-section of another design of wicking-evaporativedevice 220 based on the first material and the second material inaccordance with an embodiment of the present invention. In thisembodiment, evaporative media 508 are shorter in height than wickingsheets 510. When placed in a condensate tray, wicking sheets 510 arepartially submerged in the water but evaporative media 508 remain abovethe highest level of the condensate in the tray (line marking 512indicates the top water level in the tray) and hence do not make directcontact with the condensate in the tray. Consequently, in thisembodiment evaporative media 508 are primarily used for distributing theconcentrate in the lateral direction.

While FIG. 5A and FIG. 5B illustrate two embodiments of interspersingthe first material with the second material to form thewicking-evaporative device 220, other embodiments of the presentinvention may provide other configurations for interspersing the firstmaterial with the second material to form wicking-evaporative device220. Hence, the present invention is not limited to the specific ways ofinterspersing the first material with the second material illustrated inFIG. 5A and FIG. 5B.

FIG. 6 illustrates a cross-section in the vertical direction (i.e., thetop-view) of an exemplary design of wicking-evaporative device 220 basedon a single or two-material wicking material in accordance with anembodiment of the present invention.

In the embodiment of FIG. 6, wicking-evaporative device 220 includes aseries of wicking sheets 602 which are arranged in a zigzag pattern fromthe cross-section view, and attached into a frame 604. Moreover, wickingsheets 602 have an extended profile in both the lateral direction andthe horizontal direction. For example, in the horizontal direction(i.e., the vertical direction on the page), the profile of wickingsheets 602 is significantly larger than the profile of wicking material402 in FIG. 4A. The result of this design creates a large surface areawhich faces incoming air 606. Hence, wicking sheets 602 serve bothwicking and evaporative functions. Because wicking sheets 602 providemore wicking and evaporative area, it is possible to build wickingsheets 602 with a lower height, such that wicking sheets 602 only reachthe lower portion of the condenser coil.

In some embodiments, wicking sheets 602 are arranged to facilitatedirecting the air blowing through wicking sheets 602 to the condensercoil. In one embodiment, wicking sheets 602 are made of a single wickingmaterial, such as PVA. Note that wicking-evaporative device 220 isplaced in a condensate tray 608 which has a large bottom profile toaccommodate wicking-evaporative device 220. Also note that the design ofFIG. 6 is for illustration purposes, and other embodiments may havedifferent numbers of wicking sheets, different angles between adjacentwicking sheets, and different width-to-thickness ratios ofwicking-evaporative device 220.

FIG. 7 illustrates an exemplary configuration of a tray 702 and awicking-evaporative device 704 in an AC system 700 in accordance with anembodiment of the present invention. In the embodiment of FIG. 7,wicking-evaporative device 704 is oriented at an angle with the verticaldirection. Because the wicking fibers in wicking-evaporative device 704are typically oriented along the orientation of wicking-evaporativedevice 704, the wicking action in wicking-evaporative device 704 followsthe orientation of wicking-evaporative device 704 rather than thevertical direction. Note that this assembly is useful when theorientation of the condenser coil 706 in AC system 700 is tilted, asshown in FIG. 7. Generally, wicking-evaporative device 704 can beoriented in any tilt angle between the vertical direction and thehorizontal direction so that the wicking action can also occur at thatangle.

Embodiments of the present invention can be used in any type ofresidential or commercial AC system. One such application is in theestimated >4,000,000 rooftop cooling units (RTUs) which are commonlyused to cool non-residential buildings.

The foregoing descriptions of various embodiments have been presentedonly for purposes of illustration and description. They are not intendedto be exhaustive or to limit the present invention to the formsdisclosed. Accordingly, many modifications and variations will beapparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention.

1. An air conditioning (AC) system, comprising: a condenser coil; anevaporator coil which produces condensate; and a wicking-evaporativedevice configured to wick and evaporate the condensate in the vicinityof the condenser coil.
 2. The AC system of claim 1, wherein the ACsystem further includes a tray system configured to collect thecondensate.
 3. The AC system of claim 2, wherein the tray system ispositioned at the base of the condenser coil and distributes thecondensate laterally along the width of the condenser coil.
 4. The ACsystem of claim 2, wherein the wicking-evaporative device includes afirst material which wicks the condensate upward from the tray system.5. The AC system of claim 4, wherein the wicking-evaporative device ispositioned in the tray system such that a lower portion of the firstmaterial is immersed in the condensate.
 6. The AC system of claim 5,wherein the wicking-evaporative device is positioned such that an upperportion of the first material is disposed upward above the surface ofthe condensate, and wherein the condensate is wicked from the lowerportion of the first material to the upper portion of the firstmaterial.
 7. The AC system of claim 6, wherein the upper portion of thefirst material is positioned in front of the condenser coil.
 8. The ACsystem of claim 6, wherein the upper portion of the first material ispositioned in the path of an airflow which is directed toward thecondenser coil, and wherein the airflow facilitates evaporating thecondensate which is wicked into the upper portion of the first material.9. The AC system of claim 4, wherein the first material is constructedinto a set of spaced wicking sheets which are arranged laterally alongthe width of the condenser coil.
 10. The AC system of claim 4, whereinthe first material is configured so that its dimension perpendicular tothe condenser coil is greater than the height of the first material. 11.The AC system of claim 4, wherein the first material is a wickingmaterial.
 12. The AC system of claim 11, wherein the first material is apolyvinyl alcohol (PVA)-based material.
 13. The AC system of claim 11,wherein the wicking material is made of wicking fibers.
 14. The ACsystem of claim 13, wherein the wicking fibers are oriented upward fromthe tray system.
 15. The AC system of claim 14, wherein pore sizes ofthe wicking fibers decrease with distance away from the tray system. 16.The AC system of claim 4, wherein the first material is configured towick the condensate at a rate substantially equal to a maximum expectedcondensation rate at the evaporator coil.
 17. The AC system of claim 4,wherein the first material is configured to reduce airflow resistancethrough the wicking-evaporative device.
 18. The AC system of claim 4,wherein the wicking-evaporative device includes a second material whichdistributes the condensate laterally along the width of the condensercoil.
 19. The AC system of claim 18, wherein the wicking-evaporativedevice is positioned in the tray system such that a lower portion of thesecond material is immersed in the condensate.
 20. The AC system ofclaim 18, wherein the wicking-evaporative device is positioned in thetray system such that the second material is located entirely above thesurface of the condensate in the tray system.
 21. The AC system of claim18, wherein the wicking-evaporative device is positioned such that anupper portion of the second material is disposed upward and positionedin front of the condenser coil.
 22. The AC system of claim 21, whereinthe upper portion of the second material is positioned in the path of anairflow which is directed toward the condenser coil, and wherein theairflow facilitates evaporating the condensate which is spread into theupper portion of the second material.
 23. The AC system of claim 18,wherein the second material includes evaporative media.
 24. The ACsystem of claim 18, wherein the evaporative media include corrugatedpaper.
 25. The AC system of claim 18, wherein the second material isconfigured to distribute the condensate laterally at a ratesubstantially equal to a maximum expected condensation rate.
 26. The ACsystem of claim 18, wherein the second material is configured to reduceairflow resistance through the wicking-evaporative device.
 27. The ACsystem of claim 18, wherein the first material is distributed in auniform pattern within the second material.
 28. The AC system of claim18, wherein the wicking-evaporative device is constructed intoalternating layers, wherein a pair of adjacent layers includes a firstlayer made of the first material and a second layer made of the secondmaterial, and wherein the first layer and the second layer are incontact with each other.
 29. The AC system of claim 18, wherein thefirst material is interspersed with the second material.
 30. The ACsystem of claim 18, wherein a combination of the first material and thesecond material is configured to minimize airflow resistance.
 31. The ACsystem of claim 18, wherein the first material and the second materialare the same type of material.
 34. The AC system of claim 2, wherein thetray system has a capacity substantially equal to a maximum expectedvolume of surplus water accumulated when a condensation rate at theevaporator coil exceeds an evaporation rate at the wicking-evaporativedevice.
 35. The AC system of claim 1, wherein the wicking-evaporativedevice is configured to wick the condensate at an angle which is withina range from the vertical direction and the horizontal direction. 36.The AC system of claim 1, wherein evaporating the condensate in thevicinity of the condenser coil facilitates cooling the condenser coil.37. The AC system of claim 1, wherein evaporating the condensate in thevicinity of the condenser coil eliminates a need for piping to drain thecondensate away from the AC system.
 38. A method for removing condensatecollected from an evaporator coil within an air conditioning (AC)system, comprising: wicking the condensate upward into evaporative mediawhich is positioned in the path of an airflow directed toward acondenser coil of the AC system, wherein the evaporative media and theairflow facilitate evaporating the condensate in the vicinity of thecondenser coil, thereby eliminating a need for piping to drain thecondensate away from the AC system.